In the fields of electrical communication and digital television requiring ultra-high-speed signal transmission, differential signal transmission is becoming widely used, and consumer demand is for reducing the size of electronic devices used in transmitting high-speed differential signals. For example, Japanese Patent Application No. 2010-157505 discloses a conventional electrical connector for differential signal transmission. In this electrical connector, contact portions responsible for contacting an inserted mating connector are arranged in two rows in a mating connector receiving passageway to reduce the size of the electrical connector's housing. However, solder portions are arranged in one row on a side of the electrical connector to be connected to a circuit board. If the solder portions were arranged in two rows similarly to the contacts in the mating connector receiving passageway, the solder portions arranged outside would constitute an obstacle, making it difficult to perform tasks such as inspections of the soldering state of the solder portions arranged inside the connector, perform repairs of soldering, etc. To prevent this problem, the solder portions are surface-mounted in a single row on the circuit board. The disadvantage of a single row is that the single row requires more space to accommodate than the use of two rows, which is contrary to consumer demand for smaller electronic devices.
One possible solution is to decrease the pitch of the solder portions. However, this approach also presents problems. For example, if the pitch of the solder portions to be connected to the circuit board is set to be equal to or smaller than 0.4 mm, problems such as poor soldering and interference tend to occur. Therefore, decreasing the pitch has a limitation. Thus, if the solder portions are arranged in one row while the arrangement pitch of the solder portions is kept at a predetermined value, the pitch of the contact portions is simply widened even if the solder portions are arranged in two rows in the mating connector receiving passageway. Therefore, decreasing the dimensions of the connectors has a limitation.
The present invention was made in view of the problems described above, and provides a small-sized electrical connector while keeping an arrangement pitch of solder portions to be connected to a circuit board at a predetermined value.